Popeapalooza!

America welcomed Pope Francis with a day filled with pomp and circumstance as he made his first visit Wednesday to the White House amid cheers, excited crowds and concerns over how the church’s moral agenda bumps up against the president’s politics.

Kicking off his first day ever in this country, Francis stepped before a massive and enthusiastic crowd on the White House’s South Lawn, just after 9 a.m., to address President Barack Obama with his call for heightened attention to immigration, marriage, religious liberty, climate change and the economy.

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His remarks to a crowd of more than 11,000 Wednesday morning, under clear blue skies, framed a comprehensive encouragement to the U.S., as he outlined softly, and in English — which he spoke haltingly — a social-political agenda that tracks with his own liberal commitment to global justice and change.

The pope spoke of inclusion and invoked the historic remarks of the Rev. Martin Luther King, Jr., who in his famed “I Have a Dream” speech contrasted the Constitution’s protection of “the unalienable rights of life, liberty, and the pursuit of happiness, ” which King argued in that era did not extend to all.

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But King noted, “It is obvious that America has defaulted on this promissory note.”

Said Francis: “To use a telling phrase of the Reverend Martin Luther King, we can say that we have defaulted on a promissory note, and now is the time to honor it.”

Alluding to the ongoing political crisis of immigration in the U.S., Francis described himself as an immigrant in carefully enunciated remarks that showed he would not shy away from engaging in a tough debate.

“As a son of an immigrant family, I am happy to be a guest in this country, which was largely built by such families,” he said.

Francis spoke of marriage, and praised Obama’s efforts on climate change, as well as his opening doors to détente in Cuba.

“Mr. President, I find it encouraging that you are proposing an initiative for reducing air pollution. Accepting the urgency, it seems clear to me also that climate change is a problem which can no longer be left to our future generation,” the pope said. “When it comes to the care of our common home, we are living at a critical moment of history. We still have time to make the change needed to bring about a sustainable and integral development, for we know that things can change.”

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But the Argentine-born pontiff also was careful — at least at the onset of his visit —  not to dig into divides evident between the Catholic Church and the president’s political agenda, particularly on same-sex marriage, even as his words wield great power around the world. Some analysts expect his tone to deepen as he speaks before lawmakers Thursday during a joint session of Congress.

“American Catholics are committed to building a society which is truly tolerant and inclusive, to safeguarding the rights of individuals and communities, and to rejecting every form of unjust discrimination,” the pope said.

As pundits dissected his remarks, it was clear that many were simply excited that the pope was making his first trip to the United States.

Noted CNN’s senior Vatican analyst John Allen of the pope’s tone: “Catholic social teaching literally defies the social and political teachings of American politics.”

Obama welcomed the pope with a spiritual tone. “What a beautiful day the Lord has made,” he said.

But his remarks quickly turned political, even as he never used the word “immigration.”

“You call on all of us, Catholic and non-Catholic alike, to put the ‘least of these’ at the center of our concerns,” Obama said.

“You remind us that in the eyes of God our measure as individuals, and our measure as a society, is not determined by wealth or power or station or celebrity, but by how well we hew to Scripture’s call to lift up the poor and the marginalized to stand up for justice and against inequality, and to ensure that every human being is able to live in dignity — because we are all made in the image of God,” Obama said.

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As pundits dissected his remarks, it was clear that many were simply excited that the pope was making his first trip to the U.S. “We love you, Pope Francis,” one man screamed at the South Lawn event.

The pope then left the White House for a motorcade tour around Washington’s National Mall. He waved and smiled broadly to loud cheers as well-wishers lined the streets to catch a glimpse of Francis in his glass “Popemobile.” At one point a small girl approached him, handpicked by his security team, and the pope also kissed babies who were brought to him.

“It very much looks like an inaugural parade and you have the same security,” noted CNN’s John King of safety coordination across the city during the visit.

Amid the hoopla, for some Washington commuters, however, the morning drive slagged to a standstill, even as government employees and others were urged to work from home.

Francis, whose given name is Jorge Mario Bergoglio, is 78. He was elected pope in March 2013 after the surprise — and rare — resignation of Pope Benedict in February 2013, which came in the wake of the church’s child sex abuse scandal.

Since then, Pope Francis’s humble spirit, disdain for the wealthy trappings of the Vatican, and living by example for his followers has led to his nickname as “the people’s pope.”

His visit has drawn wide excitement from U.S. Catholics. His first full day in the U.S., after arrived Monday at Andrews Air Force Base, kicked off when he emerged around 8:45 a.m. from the Vatican Embassy, a five-minute drive from the White House.

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The friendly pontiff quickly greeted the throng gathered behind a fence, chatting and blessing many of who craned for his attention and embrace. He then, in a nod to his papal home, got into a tiny Italian-made Fiat — rather than an SUV or limousine — to make his drive to the White House.

Amid the hoopla, for some Washington commuters, however, the morning drive slagged to a standstill, even as government employees and others were urged to work from home.

Also on the pope’s schedule Wednesday was a prayer service with U.S. bishops at St. Matthew’s Cathedral and later in the afternoon, a Spanish-language mass for about 25,000 Catholics at the Basilica of the National Shrine of the Immaculate Conception, marking the first canonization mass to ever take place on U.S. soil.

Francis is set to address a joint session of Congress at 10 a.m. Thursday, followed by a visit with parishioners serving a Catholic Charities program.

The pope’s trip to Washington kicks off a six-day stay in the U.S. It will also include time in Philadelphia and New York City.

Choppers chattered loudly above downtown Washington, D.C., as news outlets scrambled to get footage of the pope in action. Drivers in cars and bike riders found plenty of road closures that made an already dreadful commute more dreadful. Joked AAA Mid-Atlantic: Travel inside the city could be “apope-calyptic.” Traffic reporters described the morning travel influx as light.

Meanwhile, as workers complained, the city took on the festive and gussied-up aura of an inauguration as plenty of yellow and white Vatican flags flew around the city to honor the pontiff’s visit.

Social media also got into the fun, with Snapchat setting up a special Popemobile filter featuring a cartoon-festooned photo frame of the pope in his “Popemobile” and the words: “They see me rollin’ — Pope Francis in D.C.” New hashtags also abounded with #PopeinDC and #Popeswag the most popular on Twitter.

Amanda House and Elisa Cipollone, both of LifeZette, contributed to this report.